The overall goal of this work is to determine the agents involved in regulation of substance P and calcitonin gene-related peptide (CGRP) release from sensory neurons and their mechanisms of action. Increasing evidence suggests that activation of sensory neurons and concomitant release of substance P or CGRP are involved in pain, inflammation and arthritic disorders. Eicosanoids (prostaglandins and leukotrienes) also appear to be important substrates in the initiation of pain and inflammation. Although the mechanisms by which eicosanoids act remains unknown, evidence clearly indicates that they can activate or facilitate activation of nociceptive sensory neurons. The purpose of the proposed experiments is to determine if selected prostaglandins and leukotrienes directly stimulate and/or facilitate the release of the putative neurotransmitters, substance P and CGRP from sensory neurons. Peptide release will be studied using two experimental models, in vitro release from spinal cord slices and release from rat sensory neurons grown in cell culture. Substance P and CGRP will be measured by radioimmunoassay. Direct stimulating effects of eicosanoids will be determined by measuring the amount of each peptide released from spinal cord slices or from neurons grown in culture exposed to various concentrations of eicosanoids in the absence of other stimulating agents. Facilitation of release will be assessed by comparing concentration- response curves for potassium and capsaicin in the presence and absence of eicosanoids. Experiments will also be performed to assess the involvement of adenosine 3',5' monophosphate (cyclic AMP) in regulation of peptide release. Cyclic AMP in cells will be measured in the presence and absence of stimulating concentrations of eicosanoids. In addition, intracellular concentrations of cyclic AMP will be manipulated to determine if these manipulations alter eicosanoid effects on release. These studies will determine whether eicosanoids can directly activate sensory neurons. They also will determine if eicosanoids have actions in sensory nerve terminals in the spinal cord. Knowledge of which substances alter activity of sensory neurons and their mechanisms of action are important for understanding the processes of pain and inflammation and in designing drugs for use in the clinical management of arthritic disorders. The proposed experiments provide a model system for studying the interactions between substrates involved in inflammation and sensory neurons and should provide new information regarding the regulation of neurotransmitter release from those neurons.